Many industries use trucks for the transportation of their goods. To transport a liquid, a truck is provided with a transport tank mounted to a frame of the truck or to a trailer of the truck. When the liquid is to be transported under pressure, the transport tank needs to be constructed to withstand this pressure. One example of such a liquid is a liquefied petroleum gas, such as propane. Typically, in order to withstand internal pressures, transport tanks are made of metal, such as carbon or stainless steel, and have a cylindrical central section and two generally curved ends. Although metal transport tanks such as the one described above are suitable for the transport of pressurized liquids they have some drawbacks.
In most jurisdictions, the total truck weight (truck plus payload) or total trailer weight (trailer plus payload) is not allowed to exceed a predetermined maximum weight. As a metal transport tank is heavy, the maximum weight of the payload that can be transported is less than could otherwise be transported if the transport tank was lighter. Also, a metal transport tank tends to corrode over time which requires maintenance, repair, and in some cases replacement of the tank.
One solution to at least some of the above-mentioned drawbacks of metal transport tanks consist is making the transport tank out of composite material. For tanks of the same volume, composite transport tanks are lighter than metal transport tanks. As a result, by using a composite transport tank the maximum weight of the payload that can be transported can be increased. Also, composite materials are typically less susceptible to corrosion than metals.
In order to fill and empty a transport tank, a number of features are provided on the tank body to permit the attachment of pipes and pumps. Similar features are also provided to permit the attachment of various gauges providing information such as internal temperature and pressure of the transport tank.
In metal transport tanks, apertures are made inside the tank body and fittings made of metal, such as steel, are inserted into the apertures. The fittings are then welded to the tank body, which simultaneously connects the fittings to the tank body and provides a seal between the fittings and the tank body.
However, in composite transport tanks this arrangement cannot be used. As would be understood, metal fittings cannot be welded to a composite material tank body. Furthermore, metals and composite materials have different material properties which means that they have different allowable stresses and different thermal coefficients of expansion. As such, providing a connection and a seal between a metal fitting and a composite tank body cannot be achieved in the same manner as in a metal transport tank. Additionally, cutting an aperture into a composite tank body creates a stress concentration in the material adjacent to the aperture due to loadings and internal tank pressure, thus weakening the transport tank in the area of the aperture.
Therefore, there is a need for a transport tank for mounting to a truck which is made of composite material and provides at least one feature for connecting at least one of a pipe, a pump, a gauge or other element to the tank.